How to Dry Oregano: Methods, Temperatures and What Drying Changes

Oregano is one of the herbs most worth drying. America’s Test Kitchen lists it first among the herbs that work well dried,¹ and across ATK’s tests of 24 recipes it was the one case where tasters preferred the dried herb: dried oregano won in chili.² The fastest reliable method is a dehydrator. Hanging small bundles works where the air is dry, but the extension guides disagree on how easily oregano air-dries, so that is laid out below rather than smoothed over.

At a glance

Before you start

The extension guides agree on timing: the best point to harvest most herbs for drying is just before the flowers first open,³⁶ picked in the early morning once the dew has evaporated.⁶ Oregon State adds that cut herbs should not lie in the sun or sit unattended after harvest.⁶

Rinse the stems in cool water and shake off the excess,⁴³ then remove all visible water with towels or paper towels.⁵ A widely repeated claim says rinsing rids herbs of pathogens; the extension guides present it as cleaning and make no such claim.

Is oregano easy to air-dry? The guides disagree

We have not picked a side. Tennessee’s wording closely follows NCHFP’s, so this is nearer one view against another than two against one, and none of the guides reports testing oregano. The cautious reading (Method) is to treat oregano as a herb that can mold: if your house is humid, use a dehydrator; if you air-dry, keep bunches small and check them for mold.

Dehydrator

NCHFP’s instructions are to preheat with the thermostat at 95–115°F, going as high as 125°F where humidity is high, and to expect 1–4 hours, checking periodically.³ Penn State’s range tops out lower, at 110°F.⁴ A common rule says never to go above 125°F; that matches the top of NCHFP’s range, which it gives for humid conditions only.³ Spread the sprigs in a single layer and start checking at the one-hour mark (common practice).

Air-drying

The Wisconsin method for sturdy herbs: tie washed branches into small bundles of 5–6 stems and hang them upside down in a warm (70–80°F), dry, well-ventilated place out of direct sunlight until the moisture has gone, generally 2–4 weeks.⁵ For herbs it treats as tender, Oregon State instead hangs small bunches inside a paper bag with vent holes cut in the top and sides, which usually takes 5–10 days.⁶ Either way, keep bundles small: the University of Tennessee warns that herbs in bundles that are too large will mold.⁷ Stripped leaves can also dry in a single layer on a screen or tray in a warm, dry room.⁵

Penn State says to keep drying herbs away from the sink, stove and dishwasher, where the air is moist,⁴ and NCHFP says drying indoors usually gives better color and flavor than drying outdoors.³ Oregon State suggests an attic, a kitchen or any warm place with air circulation.⁶ A paper bag punched with holes keeps dust off,⁴ and the Wisconsin guide says to pick one big enough that the leaves don’t touch its sides.⁵ A common claim says a bag shields the leaves from light and so prevents discoloration; we found no source that says so, though the Wisconsin guide does say to dry out of direct sunlight.⁵

Oven

Penn State’s method is the lowest temperature, not above 180°F, for 3 to 4 hours with the door open,⁴ and the Wisconsin guide gives the same figures, with the herbs in a single layer and stirred now and then.⁵ Oregon State warns that drying herbs at too high a temperature can cause flavor loss.⁶ Twenty minutes at 200°F, a method that circulates widely, appears in none of the extension guides we checked.

If your oven can’t hold 180°F or lower, use the cool-oven method. Lay leaves on a paper towel so they don’t touch, cover with another towel and another layer of leaves, and repeat for up to five layers. Leave them overnight in an oven warmed only by the light of an electric oven or the pilot light of a gas one.³⁷

Microwave

The microwave is fast and suits small amounts only.³ The guides do not agree on the timing:

As a starting point (Method), begin with a minute or less, then check every 30 seconds until the leaves crumble.

Two safety points apply whatever the timing. Penn State warns that if the load is too small, the paper towels can catch fire,⁴ and Oregon State says not to use paper towels made from recycled paper, which can contain metal scraps that arc.⁶ The Wisconsin guidance calls the microwave a last resort that cooks the herbs and gives very poor quality, and notes that the heat drives off some of the oils along with the water, so microwaved herbs may taste less intense than herbs dried other ways.⁵

Where the guides disagree

None of these was tested side by side on the same herb, so we have not picked a winner. Where a range is given, starting low and checking often is the cautious reading (Method).

What drying does to oregano

A 2022 Italian study dried oregano in shade, in a static oven, with three microwave treatments and with an osmotic treatment, and compared the essential oils with oil from the fresh plant.⁸

• Carvacrol was the main compound throughout, at 56.2–81.4% of the oil.⁸
• After drying, the shares of carvacrol, isoborneol and linalool rose significantly, and the shares of p-cymene, γ-terpinene and α-pinene fell.⁸
• Microwave and shade drying gave the highest oil yields.⁸

These are shares of the oil, not amounts in a teaspoon, and the study ran no taste test. In the kitchen, ATK found that its tasters preferred fresh herbs in every application but one; the exception was chili, where dried oregano was the favorite.² A common claim says oregano is “improved” by drying in general. The evidence is narrower: ATK found that dried oregano fared reasonably well in dishes cooked for more than 20 minutes with a good amount of liquid, and it won one test, in chili.²

How to tell it’s done

Herbs are dry when the leaves are crisp and crumble easily between the fingers⁴ and the stems break when bent.³ Oregon State adds that the leaves should fall from the stems.⁶ Strip the leaves and discard the stems.⁵

Check your work after packing. The Wisconsin guidance is to watch the filled containers for a couple of days; if you see any moisture, take the herbs out and dry them longer.⁵

Air-dried herbs can carry insects. The University of Tennessee says air-dried herbs and seeds need treating to kill insects and their eggs, either by heating at 160°F for 30 minutes or by freezing at 0°F or lower for at least 48 hours, and it recommends freezing for better flavor.⁷

Storing dried oregano

Keep the leaves whole and crumble them as you cook; Penn State says storing herbs whole is preferred.⁹ Use airtight containers in a cool, dry, dark place,³ away from the stove and sink.⁴ Oregon State adds that dried herbs can also go into airtight containers in the freezer.⁶

How long dried oregano keeps depends on whom you ask, and none of these figures was measured on oregano:

We have not averaged these. McCormick defines shelf life as how long spices stay most aromatic,¹⁰ which is the right way to read every figure here: a quality window, not a safety date. The practical test is smell. Crush a pinch, and if the aroma is faint, the oregano has faded.

Herbs in oil are a separate food-safety question. A 2011 review of home-prepared vegetables and herbs stored in oil advises refrigerating them and using them within four days or discarding them, and calls freezing the safest option.¹¹

Not yet measured

• Whether oregano molds more readily than other herbs when air-dried; no guide we found tested it.
• How long home-dried oregano keeps, measured on oregano rather than herbs in general.
• Microwave times by oven wattage for oregano.

Related

• Oregano
• Fresh oregano vs. dried
• Can you freeze oregano?
• Oregano substitutes
• Cooking with oregano
• Marjoram vs. oregano
• Mexican oregano vs. oregano
• How to dry marjoram
• How to rehydrate herbs

Footnotes

1. When You Should Actually Use Dried Herbs, America’s Test Kitchen. americastestkitchen.com · Publication ↩ ↩² ↩³

2. Science: Substituting Dried Herbs for Fresh, America’s Test Kitchen. americastestkitchen.com · Publication ↩ ↩² ↩³

3. Herbs (drying), National Center for Home Food Preservation. nchfp.uga.edu · Reference work ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷

4. Let’s Preserve: Drying Herbs, Penn State Extension. extension.psu.edu · Reference work ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷

5. Drying Herbs, Wisconsin Master Gardener Program, University of Wisconsin-Madison. mastergardener.extension.wisc.edu · Reference work ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶

6. Drying herbs (SP 50-921), Oregon State University Extension Service. extension.oregonstate.edu · Reference work ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵

7. Drying Herbs, University of Tennessee Extension. lawrence.tennessee.edu · Reference work ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

8. Caputo et al., Scientific Reports, 2022 (abstract). doaj.org · Peer-reviewed ↩ ↩² ↩³ ↩⁴

9. Preserving Herbs by Drying, Penn State Extension. extension.psu.edu · Reference work ↩

10. How Long Do Spices Last?, McCormick. mccormick.com · Merchant ↩ ↩²

11. Nummer et al., Food Protection Trends, 2011. foodprotection.org · Peer-reviewed ↩